remove arguments option in `go`

I have a good proposal for error handling I think, but one thing that it does is gives you the ability to configure a `go` block to automatically propagate. I don't think we should add tons of options to go functions, but this is useful enough to merit it. It should look like:

```js
go(function*() {
  // ....
}, { propagate: true });
```

Right now you'd always have to pass an empty array as the second argument. I've always found that argument redundant though since we have `spawn`. Either just use those variables directly in the go block, or use spawn to call the generator with the args, like `spawn(gen(arg1, arg2))`. In the rare case that you need to use this with a new function, just do `spawn((function*(x, y, z) { ... })(x, y, z))`.

Removing this gives us the ability to add the above option (which I will go into more details in the errors PR), without removing hardly any functionality. What do you think?